Industry standards suggest a minimum of 18F inside to outside temperature is required to locate insulation issues. This is conservative. Newer, more sensitive imagers may require less. Thermally "thicker" walls may require more.

Yes, HVAC can be used to warm or cool the interior but the temperature difference is best when stable for a period of time or else thermal capacitance comes into play, often in confusing ways.

The best views of wall insulation is typically from the interior of the building where the wind and sun are less of a factor (but not always insignificant) and things are more thermally "connected" to the insulation.

I'd be happy to send you an article I co-authored several years ago that should help you get started; I tried to post it but could not. Go slowly until you gain some confidence and expertise. You may also want to look over the new RESENT Guideline (I can also send this or you can find it online) which covers the whole process from that point of view.

Here is a picture of missing insulation. This is a master bedroom. The orange on the right wall is full of windows. Above the windows is wall, sun is shining; wall faces SW. Outside temp is about 45. You can see the insulation and the studs. Note at this point the depth of field has this part of the image out of focus. The other wall backs up to the Living Room. The ceiling has not lost direct sun exposure. It is a vault. You can see the first 2 feet of the vault from the wall up are bright orange. Then it goes green and blue showing less heat coming through.

I did nothing unusual with the home. The blower door was running at the time of this picture. I was spending some extra time in the area, because the HO complaint was hot in summer, cold in winter.

Visual inspection of the attic above, showed the vault had enough insulation, but it was all piled on the peak, it had not been spread to the edges. Blown FG. The attic insulation card said R-30. The house was built in 1998.

I believe I could have gotten a very similar image with an outside temp of 60+ if the sun had been shining. This would not follow guidelines. I did verify the IR with a visual inspection. That assisted in identifying the problem, and writing an effective specification to solve it. I would work for a large delta T for verification, since I don't want to walk in the attic and compress the insulation.

No disrespect meant here, but before you would use the IR camera on an inspection or audit, you need to become fully versed on not only how to use it, but also on building science and thermography. You should take classes on thermography.

A temperature differential (delta T) between the outside and the inside is recommended, otherwise it is difficult when the temperature inside is equal to the outside. I have done inspections when there was only a 10 degree difference, but much prefer when there is at least 16 - 20 degrees difference. Obviously 20 degrees or more difference is best.

Yes, do turn up the heat and wait for a while if it is cool outside, or turn on the AC and wait for a while if it is warm outside. Try this in yours or your family's homes firt. You have to do a bit of trial first for practice and get used to it.

Debra Monte said:

No disrespect meant here, but before you would use the IR camera on an inspection or audit, you need to become fully versed on not only how to use it, but also on building science and thermography. You should take classes on thermography.

John N. - thanks for sharing your photo and information regarding it. im a little confused, so maybe you can help me. I'm just learning. the outside temp is approx 45 degrees and the inside surface temp ranges from 67 - 68 degrees. this would provide a delta T of approximately 20+ degrees from inside to out. given the principle that inside warmer temperature would be trying to migrate to the outside cooler temperature, a surface temperature consistent with the indoor ambient temperature would be relative to the ability of the surfaces composit ability to maintain the internal ambient temp. in other words, resist the tendancy for the warmer air to migrate to the colder and therefore the surface temp would be similar to the indoor ambient temp, is that correct?

Judy; your post reflects a lot of the issues that are now going on with in the BPI training program. Instructors are focusing on the building envelope, blower door and utiizing a smoke generating device. When I went through my first class, several years ago, the instructor became annoyed with my discussion of thermal technology. I understand that the instructors are not into the additional IR training. So; you have been short changed.

There is a lot more to consider than simply pointing a thermal camera at a wall and calling out missing insulation or air leaks. We need to 'do no harm' as stated in the regulations. Look for RESNET and BPI to radically redo their training to include advanced study in Infrared technology soon.

Get a head of the curve and take a Level 1 course as soon as you can. There are some good instructors, to include the Snell Group, Infraspection Institute, that can guide you towards your goal. Make sure your instructor is up to date on BPI and RESNET criteria or you will be wasting your money.

I agree with Debra and Allen, take the Level I course. If you are BPI or RESNET Certified, how would you like people doing energy audits with no certification, but they have the tools? They may understand it and do an okay job, but the technicalities of it all make it worth your while. It is not cut and dry by ANY MEANS!! It is the only way you can reliably begin to understand what you are seeing. Do you understand what John was talking about with thermal capacitance of the materials in the house giving you a difficult to understand image or misleading image? That is what the course will help you understand! The Snell Group is who I took my course from and they really get you "thinking thermally"!!

Was your interest in IR due to the lower priced imager. Was this an online purchase or face to face with a salesperson trained in IR use? If so; did the saleperson recommend an IR course, provide training material or support?

I would not recommend anyone purchase an IR Imager prior to taking a level 1 course. You will be surprised on the vast differences in the imagers out there and that price alone is not a deciding factor for everyone. An uneducated camera purchase will be a waste of your time and money.

The temperature heat loss info seems to be correct. The IR shot is not talking about that directly. The IR measures apparent (percieved) temperature on the surface of what the camera is pointing at. You need to know the material you are imaging, its emissivity and its make up. If it is metal, or wood or glass or something with a high reflectivity; or a low e (missivity). Think low e windows.

The entire image I posted was drywall, or windows with window covering. The bedroom was dark, without lights on. There is part of a picture hanging on a wall in the image. The colors represent different surface temperatures of the various areas. So then you identify what shows up in the image. SW wall, orange is windows behind curtains, a picture, wall cavities (insulated) and studs, the sun is loading this wall. You turn the corner in the room and you move to the south east wall, back up to conditioned space on the other side. Note how much less apparent the studs are, and the wall is much more even temperature. Not much heat loss to the other room. Now move on the vaulted ceiling. Green, blue and dark orange are your primary colors here. The sun has been bearing on this ceiling for a while. So the uninsulated portion is bright orange as the heat is un-resisted. The lighter blue, shows resistance to heat. The green is in between. Think studs or areas where there is a little of the blown FG but not a lot or nothing.

Note the dark blue in the corer of the room and the corner of the vault to the wall. This is boundary layer. The air in a little bit of this 90 degree corner does not move (as much as the air along the wall as a whole). So, it cools down. Hence my earlier comment that the camera images perceived surface temperature.

None of this IR stuff negates the applied heat loss theory. It does change how it is perceived. It makes it real to the auditor, he/she then can go looking for the problem apparently revealed. It makes it real to the HO so they have confidence in the recommended improvement.

The temperatures in the image range from 62 (at the intersection of three corners) to 68 over on a wall cavity that abuts conditioned space. So that is closer to the ambient inside temperature. Remember the convective cooling effect because I had the blower door running. Because this insulation was on a vault, the outside image would have not shown anything.

When you take your Level I class, you will learn about qualitative VS quantitative processes. This image is a good quantitative image.

dale garren said:

John N. - thanks for sharing your photo and information regarding it. im a little confused, so maybe you can help me. I'm just learning. the outside temp is approx 45 degrees and the inside surface temp ranges from 67 - 68 degrees. this would provide a delta T of approximately 20+ degrees from inside to out. given the principle that inside warmer temperature would be trying to migrate to the outside cooler temperature, a surface temperature consistent with the indoor ambient temperature would be relative to the ability of the surfaces composit ability to maintain the internal ambient temp. in other words, resist the tendancy for the warmer air to migrate to the colder and therefore the surface temp would be similar to the indoor ambient temp, is that correct?

You are absolutely correct. Combining qualitative info with quantitative info gives you the tools to clearly demonstrate to your customer the deficiencies of their building envelope and insulation. Of course, using a blower door in conjunction with the IR imager means that your pictures now POP, and that the temperature differential between indoor and outdoor becomes less signifigant. Nowadays, most blower door software has built in reports that you can submit to your customer with the imagery to create a very complete analysis and report.